Web.config custom errors not working for 404's

Question

<customErrors mode="On" defaultRedirect="~/Error.aspx">
    <error statusCode="500" redirect="~/500/"/>
    <error statusCode="404" redirect="~/404/"/>
</customErrors>

This works fine for requests like:

~/egerg.aspx
~/wf92734eg.aspx

But for any other extension, this gives a server 404 page! How can I make the server 404 page redirect to my error page?

Answer 1

This solution works on my website which is 99% webforms and 1% Razor/MVC 4 on .NET Framework 4.

1. In /Web.config:

   <system.web>
     <customErrors mode="RemoteOnly" defaultRedirect="~/Error.aspx">
       <error statusCode="500" redirect="~/500/"/>
       <error statusCode="404" redirect="~/404/"/>
     </customErrors>
   </system.web>
   

2. In the Page_Load event of your 404 handler (/404/default.aspx.cs, I assume):

   protected void Page_Load(object sender, EventArgs e)
   {
       Response.StatusCode = 404;
       Response.TrySkipIisCustomErrors = true;
   }
   

3. Repeat the last step for the 500 handler.

4. The Application_Error method is empty in /Global.asax.cs.

This solution is very similar to this one.